Diesel engine water pump with thrust bearing preload

ABSTRACT

An improved diesel engine water pump includes three main features that aid in extending the maintenance free life of the pump. The impeller shaft is carried by tapered roller shaft support bearings of which the impeller bearing has a floating outer race that is urged axially by a preload spring to provide a prescribed axial preload that maintains concentricity of the shaft with the axis and prolongs bearing life. An improved oil seal combines an oil slinger, a stationary deflector and a lip oil seal with a return passage to the engine to more effectively limit oil leakage from the pump. An improved water seal includes pressurized water jets fed from the pump volute that flush wear particles from the water seal surface and increase water seal life. Further details of these features are also disclosed.

TECHNICAL FIELD

This invention relates to water pumps of the centrifugal impeller typeintended primarily for use in diesel engine cooling systems, especiallyfor railroad locomotives, but also useful for other purposes.

BACKGROUND OF THE INVENTION

It is known in the art relating to diesel engine cooling systems toprovide an engine with one or more centrifugal water pumps, each havinga centrifugal flow or mixed flow impeller carried on a shaft and drivenby a drive gear or other drive means. The shaft is supported on spacedbearings carried in a housing and lubricated by oil flow from theassociated engine oil system. Both ball and roller bearings have beenused in the past to carry rotary support loads and axial thrust forcesacting on the shaft.

Oil passing through the impeller end bearing is returned to the engineoil sump through a drain line or passage in the water pump housing. Alip-type oil seal is conventionally utilized to prevent oil from passingalong the shaft into the water impeller portion of the pump. Similarly,a conventional cartridge-type carbon water seal running against anannular seal surface has been used to prevent the escape of pressurizedwater from the impeller end of the pump into the oil lubricatedportions.

SUMMARY OF THE INVENTION

The present invention provides an improved water pump constructionincluding multiple features which combine to provide increased operatinglife for the supporting and wearing components of the pump.

The bearings utilized for support and thrust loads are preferablytapered roller-type bearings including a drive bearing at the drive gearend for accepting drive forces and major thrust loads developed in theimpeller. An impeller tapered roller bearing is mounted in the housingtoward the impeller end and includes an inner race spaced a fixeddistance from the inner race of the drive bearing, the outer race ofwhich is fixed in the pump housing.

The outer race of the impeller bearing is mounted to be axially slidablein the housing. A spring element, such as a wave spring, is mounted inthe housing and biases the outer race in a direction to provide acontrolled preload on the roller bearings. The spring maintains thebearings in a controlled preload condition which is sufficient to absorbminor reverse thrust loads which may occur in the pump. The preloadincreases bearing life by maintaining shaft concentricity and avoidingrunout, or eccentric rotation of the shaft, which could increase bearingloads and generate wear problems.

A further feature is the additional of an oil slinger mounted on theinner race of the impeller bearing and adapted to centrifugally directoil passing thorough the adjacent bearing into an annular collectorgroove. The groove carries the oil to the internal oil drain passage ofthe pump. Any oil escaping past the oil slinger contacts a deflectorwhich also directs oil toward the oil drain passage. The deflector formspart of an oil seal including a conventional lip seal for preventing anyremaining oil reaching the seal from passing through to the water sideof the pump.

Still an additional feature of the improved water pump is a water sealwhich includes a stationary seal member mounted in the housing andhaving an annular seal surface formed on a radial wall. A rotatable sealmember of conventional construction rotates with the impeller andengages the radial seal surface to prevent water from behind theimpeller from escaping into the oil lubricated portion of the pump.

Seal life is improved by the addition of a seal flush arrangement whichreceives high pressure water from the pump volute at the outlet of theimpeller and directs it through angled orifices or nozzles in acylindrical wall of the stationary seal member. The nozzles spraypressure water against the outer portion of the seal surface to flushaway particles of debris from seal wear. This reduces the collection ofwear particles remaining on the seal surface and embedding in the seal.Removal of the wear particles thus increases the wear life of the seal.

These and other features and advantages of the invention will be morefully understood from the following description of certain specificembodiments of the invention taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The single FIGURE of the drawing is a cross-sectional view along thelongitudinal axis of the pump and illustrating the various improvedfeatures of a water pump according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings in detail, numeral 10 generally indicatesa water pump of the centrifugal type adapted for use in diesel enginecooling systems or other suitable applications. Pump 10 includes ahousing 12 containing a shaft 14 rotatable on an axis 16 extendingthrough the housing. The shaft mounts a drive member in the form of agear 18 that is carried adjacent a drive end 20 of the housing 12.

A centrifugal impeller 22 is mounted on an opposite end of the shaftadjacent an impeller end 24 of the housing. The impeller is containedwithin a volute 26 that is carried on the impeller end of the housing.The volute includes an axial inlet opening 28 and a radial outlet 30 todirect water or other coolant into vanes 32 of the impeller. These drawthe water axially into the impeller and expel it radially into theassociated volute for discharge to an external cooling system.

The pump shaft 14 is supported in the housing 12 by a pair ofaxially-spaced tapered roller bearings including a drive bearing 34 andan impeller bearing 36. The drive bearing 34 is designed to accept majorrotational loads applied to the gear 18 as well as primary thrust loadsresulting primarily from the axial flow of the water drawn in by thewater pump and expelled radially. Bearing 34 includes an outer race 38fixed within the housing 12 and an inner race 40 mounted on the shaft14. The impeller bearing 36 carries primarily centrifugal loads andreverse thrust loads from the impeller, which are limited in force.

Bearing 36 also has an outer race 42 carried in the housing and an innerrace 44 mounted on the shaft 14. The inner races 40, 44 of the bearingsare fixed to the shaft along with the drive gear 18 by a nut 46 threadedon the shaft. The nut clamps the gear against the inner race 38 of thedrive bearing 34 which in turn engages a spacer tube 48 that forces theinner race 44 of the impeller bearing against a shoulder 50 on theshaft. This fixes the spacing of the bearings and clamps them solidly inposition on the shaft.

In accordance with the invention, the outer race 42 of the impellerbearing 36 is made axially slidable in the housing. A biasing element inthe form of a wave spring 52 is mounted in the housing around the shaftand engages the housing and the drive end of the outer race 42 of theimpeller. The spring biases race 42 axially toward the impeller andexerts a predetermined preload force against the outer race 42. Thispreloads both of the shaft bearings with a pre-selected axial thrustforce.

The preload force is adequate to offset any reverse thrust forces whichmay be applied against the impeller bearing while the major thrustforces are taken up by the drive bearing 34 as previously described. Thepreload wave spring 52 thus provides a minimum thrust loading on thebearings which is adequate to avoid the development of any looseness orclearance in the bearing set and thus maintains the shaft in concentricrotation around the axis 16 within the housing 12. The development ofany centrifugal forces on the bearings due to eccentric rotation of theshaft is thereby prevented so that bearing life is extended.

Bearings 34, 36 are lubricated within the housing by oil deliveredthrough a feed passage 54. The passage receives lubricating oil from alubricated portion of an associated engine on which the pump is mountedand directs the oil into an annular chamber or enclosure 56 from whichit may lubricate both bearings. The impeller bearing 34 may also belubricated by oil splash from the adjacent engine system which can alsoenter the enclosure 56 to lubricate the impeller bearing 36. Excess oilin the enclosure can escape either by passing through the drive bearing34 into the adjacent engine enclosure, not shown, or by passing throughthe impeller bearing 36 into an annular collector groove 58. The groove58 connects with a drain line or passage 60 that carries oil from thecollector groove back to the associated engine oil system for return tothe engine sump.

An oil control 61 is provided in order to prevent oil from escaping fromthe bearing enclosure 56 into the water side of the pump housing. Thecontrol may include a conventional lip seal 62 mounted in the housingfor engagement of the seal lip with a seal surface of the shaft. Toimprove the operation of the seal, the invention includes a radialdeflector 64 extending from the body of the lip seal and adapted tointercept oil splashed from the bearings and direct the oil downwardinto the oil collector groove 58 for draining to the engine system.

In addition, the pump oil control 61 includes a radial oil slinger 66mounted on the impeller end of the impeller bearing inner race 44. Theoil slinger 66 is positioned to centrifugally throw oil passing thebearing 36 and engaging the slinger into the collector groove 58, fromwhich it is directed through passage 60 to the engine lubricationsystem.

The combination of the three elements provided by the oil control 61provides a three fold arrangement for control of oil flow from theimpeller bearing to the collector and out through the drain passage 60.The conventional lip seal forms a back up to limit the passage of anyoil passing the first two elements, that is the oil slinger 66 and thedeflector 64, from escaping into the water side of the pump.

In accordance with the invention, pump 10 includes an additional featurecomprising an improved water seal assembly 68. Assembly 68 includes astationary water seal member 70 which is mounted behind the impeller inthe impeller end of the housing. Member 70 includes a cylindrical wall72 closed at one end by a radial wall 74 having a radial seal surface 76surrounding the shaft and facing toward the impeller end of the housing.

Within the stationary member 70, a rotatable water seal member 78 ismounted on the shaft 14. Member 78 includes a shaft seal 80 adjacent toa rotatable seal ring 82 that rotates with the impeller. The seal ring82 has an end engaging the seal surface 76 for preventing water flowfrom the water side of the pump into the oil lubricated areas at thedrive end of the housing. A conventional coil spring 84 extends betweenthe impeller 22 and the shaft seal 80 and biases the seal ring 82against the seal surface 76 to maintain a positive seal against leakage.

In accordance with the invention, pressurized water from the volute 26is delivered, such as through passages 86 and 88 in the volute andhousing respectively, to an annular groove or plenum 90. The plenum 90connects with angled orifices or nozzles 92 extending thorough thecylindrical wall 72 of the stationary water seal member 70. The nozzles92 are aimed in the direction of the radial seal surface 76.

In operation of the pump, rotation of the seal ring 82 against the waterseal surface 76 causes wear particles of the ring to be dislodged fromtime to time and collect adjacent the ring 82 on the seal surface. Theparticles are dislodged and carried away from the seal surface by highpressure water spray which is directed from the volute supply source tothe annular groove or plenum 90 and through the nozzles 92 against theseal surface surrounding the ring 82. The seal surface 76 is therebymaintained clear of wear particles which would otherwise collect aroundthe surface and impair the wear life of the seal ring. Accordingly, thelife of the seal ring is extended and longer maintenance-free operationof the water seal is provided.

In similar fashion, the oil control 61 of the pump, including the oilslinger 66, deflector 64 and lip seal 62, provide superior oil controlwhich avoids the escape of lubricating oil into the water side of thepump. This extends the life of the lip oil seal to prevent leakage.

Finally, the wave spring 52, providing a predetermined thrust preload onthe shaft support and thrust bearings 34, 36, maintains the shaft infully concentric operation on its axis and thereby improves bearinglife. As a result, a water pump having an extended operating life withreduced need for repair is provided by the present invention.

While the invention has been described by reference to certain preferredembodiments, it should be understood that numerous changes could be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to thedisclosed embodiments, but that it have the full scope permitted by thelanguage of the following claims.

1. A water pump of the centrifugal type adapted for use in enginecooling systems, the water pump comprising: a housing containing a shaftrotatable on an axis extending through the housing, the shaft mounting adrive member adjacent a drive end of the housing and a fluid impeller atan opposite impeller end of the housing; axially spaced roller bearingssupporting the shaft in the housing, each bearing having an inner racefixed on the shaft and an outer race mounted in the housing, the outerrace of one bearing being fixed in the housing and oriented to transmitmajor thrust forces from the shaft to the housing and the outer race ofthe other bearing being axially slidable in the housing and oriented totransmit minor thrust forces to the housing; and a biasing elementdisposed axially between the bearings and acting between the housing andthe axially slidable outer race to preload the other bearing in adirection away from the one bearing with a selected preload forcemaintained on the other bearing, thereby preloading both bearings with aminimum preload force to maximize bearing life and concentric rotationof the shaft over all operating conditions of the pump.
 2. A water pumpas in claim 1 wherein said one bearing is a drive bearing fixed in thedrive end of the housing adjacent the drive member and the other bearingis an impeller bearing spaced a fixed distance from the drive bearingtoward the impeller end of the housing.
 3. A water pump as in claim 2wherein the outer race of the impeller bearing is biased toward theimpeller end of the housing.
 4. A water pump as in claim 1 wherein thebiasing element is a spring.
 5. A water pump as in claim 4 wherein thespring is a wave spring.
 6. A water pump as in claim 4 wherein the drivemember is a gear adapted for engaging a driving gear in a lubricatedenclosure of an associated engine.
 7. A water pump of the centrifugaltype adapted for use in engine cooling systems, the water pumpcomprising: a housing containing a shaft rotatable on an axis extendingthrough the housing, the shaft mounting a drive member adjacent a driveend of the housing and a fluid impeller at an opposite impeller end ofthe housing; axially spaced roller bearings supporting the shaft in thehousing, each bearing having an inner race fixed on the shaft and anouter race mounted in the housing, the outer race of one bearing beingfixed in the housing and oriented to transmit major thrust forces fromthe shaft to the housing and the outer race of the other bearing beingaxially slidable in the housing and oriented to transmit minor thrustforces to the housing; and a biasing element acting between the housingand the axially slidable outer race and preloading the other bearingwith a selected preload force maintained on the other bearing tomaximize bearing life and concentric rotation of the shaft over alloperating conditions of the pump; wherein the bearings are mounted in anoil lubricated recess of the housing and the recess includes an oilcontrol, the oil control including: an oil slinger mounted on therotatable shaft adjacent the impeller bearing and operative tocentrifugally direct oil from the impeller bearing into a collectorconnected with an oil return passage.
 8. A water pump as in claim 7wherein the oil control further includes: a stationary oil seal having adeflector extending inward from the housing adjacent the oil slinger andoperative to deflect bypassed oil into the return passage; and a seallip engaging the shaft and blocking the passage of bypassed oil alongthe shaft toward the fluid impeller.
 9. A water pump of the centrifugaltype adapted for use in engine cooling systems, the water pumpcomprising: a housing containing a shaft rotatable on an axis extendingthrough the housing, the shaft mounting a drive member adjacent a driveend of the housing and a fluid impeller at an opposite impeller end ofthe housing; axially spaced roller bearings supporting the shaft in thehousing, each bearing having an inner race fixed on the shaft and anouter race mounted in the housing, wherein one bearing is a drivebearing fixed in the drive end of the housing adjacent the drive memberand the other bearing is an impeller bearing spaced a fixed distancefrom the drive bearing toward the impeller end of the housing, the outerrace of said one bearing being fixed in the housing and oriented totransmit major thrust forces from the shaft to the housing and the outerrace of the other bearing being axially slidable in the housing andoriented to transmit minor thrust forces to the housing; a biasingelement acting between the housing and the axially slidable outer raceand preloading the other bearing with a selected preload forcemaintained on the other bearing to maximize bearing life and concentricrotation of the shaft over all operating conditions of the pump; avolute connected with the impeller end of the housing for receivingpressurized water from the impeller; a stationary water seal membermounted behind the impeller in the impeller end of the housing andincluding a cylindrical wall connecting at one end with a radial wallhaving a seal surface surrounding the shaft; a rotatable water sealmember mounted on the shaft and engaging the seal surface to preventwater leakage toward the lubricated recess of the pump; at least onepassage connecting the volute with a plenum adjacent the cylindricalwall; and nozzle passages through the cylindrical wall and aimed todirect water jets against the seal surface to carry away worn particlesfrom the seal surface and thereby increase the wear life of the waterseal members.
 10. A water pump as in claim 7 wherein said one bearing isa drive bearing fixed in the drive end of the housing adjacent the drivemember and the other bearing is an impeller bearing spaced a fixeddistance from the drive bearing toward the impeller end of the housing.11. A water pump as in claim 7 wherein the outer race of the impellerbearing is biased toward the impeller end of the housing.
 12. A waterpump as in claim 7 wherein the biasing element is a spring.
 13. A waterpump as in claim 12 wherein the spring is a wave spring.
 14. A waterpump as in claim 12 wherein the drive member is a gear adapted forengaging a driving gear in a lubricated enclosure of an associatedengine.
 15. A water pump as in claim 9 wherein said one bearing is adrive bearing fixed in the drive end of the housing adjacent the drivemember and the other bearing is an impeller bearing spaced a fixeddistance from the drive bearing toward the impeller end of the housing.16. A water pump as in claim 9 wherein the outer race of the impellerbearing is biased toward the impeller end of the housing.
 17. A waterpump as in claim 9 wherein the biasing element is a spring.
 18. A waterpump as in claim 17 wherein the spring is a wave spring.
 19. A waterpump as in claim 17 wherein the drive member is a gear adapted forengaging a driving gear in a lubricated enclosure of an associatedengine.